docs: def keys_in_dict(d, parent_key, keys):
      """
      Create a list of keys from a dict recursively.
      """
      for key, value in d.iteritems():
          if isinstance(value, dict):
              keys_in_dict(value, key, keys)
          else:
              if parent_key:
                  prefix = parent_key + "."
              else:
                  prefix = ""
  
              keys.append(prefix + key)
  
      return keys